one of my point was, how are you gonna ensure balance charged of that 52x 18650?
Literally exactly the same way as you do with those hobby "lipo" cells.
that lipo has already balance charge connector and that single giant connector. all you have to do is to make custom XT60 connector to series 4 of them. disconnect later to use that hobbyking turnigy balance charger to charge one at a time if he wish to, or buy 4 for simultaneus charge if he wish to. unless the OP want to emulate the lipo XT60 and dupont connectors, he is going to solder all of them fixed in parallel and series, and he is going to need 4 "floating" similar magnitude as hobbyking intelligent charger for that, no option for 1 charger only. and if that hobbyking charger is not floating (ie share common ground) then he has to make his own floating balance charger for the 52x cells. or maybe just 1 48V lion charger i dont know.
not to mention checking each single cell for damage.
You don't; like you don't check each square inch of those lipos for damage.
2 options... 1) if you have thick pocket, yes you dont have to check each cells in lipo, just buy new, throw out of spec lipo away. 2) but if we have thin pocket, we will check each cells and take out the damaged cells like i did to 2 of my 4s lipo a year ago, now they are 3S only, i sensed the other one cells are deteriorating fast too so i'm going to mod them to become 2x 2s lipo, but i think i'll combine them to become 1x 4s lipo again. but if i have thick pocket next month i'll just throw them away knowing they will fail soon enough. mostly due to my ignorance of how lipo batteries should be stored, i stored them at full charged capacity
, lipo are meant for continous heavy usage.
not to mention checking each single cell for damage.
18650 cells are especially designed to be paralleled and work as larger "cells". After all, that's how they are used in their most prominent, traditional application, laptop packs.
This is beginner's li-ion 101.
yes but they are batteries too, like the other batteries, sooner or later they will die too. batteries in general 101
furthermore he is going to buy misc 18650 from unknown seller. i will say 1 year lifetime tops, half a year under heavy usage, to all the 52 cells. my condolences to all my vaping 18650s, both cheap and branded.